This invention relates to grain milling generally, and more particularly to improved milling processes which accomplish separation of the grain components in a novel manner resulting insubstantial economic savings and increased yield. The invention also deals with an improved method and apparatus for degerminating grain such as corn.
Conventional milling techniques utilize a gradual reduction process wherein successive differential grinding and shifting separates the basic components of the whole kernel grain, namely bran, endosperm and germ. The grain is first cleaned with care being taken to maintain the grain intact. With relatively tough grains such as wheat, impact deinfestation may be utilized under proper conditions without the danger of cracking the grain. With most brittle grains such as corn under most conditions, a water wash is normally performed to remove foreign materials while protecting the grain from damage.
Using prior art procedures, the cleaned grain is then subjected to tempering wherein water absorption magnifies the differences in grinding characteristics of the grain components. Finally, the gradual reduction process subjects the grain to multiple grinding and separating steps until the components have been ground to the desired size and purity. The ground product is dried if necessary to meet market specifications, cooled and graded. A typical milling process for highly purified products utilizing conventional techniques has from 50 to 60 separate steps before the end products are reached.
In addition to the expense of the large number of rollers needed in the gradual reduction process, the stock must be elevated each time it is to be passed through another set of rollers, thus requiring expensive conveying equipment. Further, since tempering is necessary to achieve separation of the grain components, the components must be dried to the proper moisture content. Again, this increases the cost and complexity of the milling process and delays its completion. The high fat content and consequent low quality of the "fines" resulting from the conventional process necessitates that they be separated and removed from the stock, which further adds to the difficulty and expense involved.
The degree of separation of germ from endosperm that is achieved with conventional degerminating machines is lacking somewhat in completeness and this causes many of the problems that are encountered in the overall milling process. In the Beall degerminator, which is used extensively in the United States, the grain kernels are rubbed more against one another than against the metal of the machine. As a consequence, even though relatively good separation of the germ is achieved, a large quantity of fines is generated and the fines are high in fat content since they contain much germ.
Impact type degerminators are used for specific purposes such as where finished products having high fat content are acceptable (table meal) and where smaller granulation of the finished products is involved (no large grits). The impact degerminators that have been used in the past generate fewer fines than the Beall degerminator and provide higher yields of recovered oil; however, the separation of the germ that is achieved with impact machines is poor and for this reason they have not been widely used. All degerminators that have been proposed or used in the past break the germ, to some degree, and the quality of the product is thus reduced in comparison to products in which the germ is in a whole condition.
It is a primary object of the present invention to provide a method of milling grain which completes the milling process in a minimum number of steps and is therefore more economical than processes employing gradual differential grinding techniques.
As a corollary to the above object, a further objective of the invention is to provide a method of milling grain wherein the fines resulting from the degermination need not be removed in an extra separate step as is required in conventional processes. The fines from the degerminator are normally left in the stock and removed after milling together with the later germinated fines, thus eliminating the necessity for removing the degerminator fines as an added step.
It is also an important aim of this invention to provide a milling process for grain which allows the use of impact deinfestation machines on relatively brittle grain such as corn thereby eliminating the need for a water wash or gravity table cleaning and providing for substantial economic savings in the equipment utilized in carrying out the cleaning operation.
A further aim of the invention is to provide a milling process for corn which accomplishes more effective separation of the black germ tip from the endosperm as a result of reduced grinding of the whole kernel grain and thereby results in a reduced quantity of "black specks" in the end product making it of higher grade and making it more desirable for cereal grits and meal.
Yet another object of the invention is to provide a milling process for corn wherein the need for tempering the grain is eliminated in some situations and cut down in other situations. Accordingly, the expense and delay associated with drying the grain is avoided or reduced appreciably.
In conjunction with the preceding object, it is still another object of the invention to provide a milling process in which only a portion of the grain is tempered, such as the bran, so that only a portion of the grain needs to be dried.
An additional object of the invention is to provide an improved method and apparatus for degerminating grain wherein a high degree of separation of the germ is achieved without the germ being broken.
A still further object of the invention is to provide a method and apparatus for degerminating grain wherein the grain kernels are crushed from the thin edges toward the center in a manner to pop the germ component out of the kernel in a substantially whole condition.
Yet another object of the invention is to provide a degerminating apparatus of the character described which assures that crushing forces are applied only to the thin edges and not to the relatively large side surfaces.
It is also an important object of the invention to provide a degerminating apparatus wherein the impact surfaces against which the grain is impelled are adjustable thus assuring the optimum angle of attack regardless of the type of grain or the condition of it.
There are numerous other advantages and objects of the present invention which will be discussed or become apparent from a reading of the following specification and claims: